GC3/SP1 Speakers & ADC SkyBell HD?

I want to add an ADC SkyBell HD to my 2GIG system at my front door. But, SkyBell (mfr tech support) tells me that the SkyBell HD is designed to only work with one mech doorbell, which is a problem. I’m expecting the Alarm.com video from the doorbell camera to not be an issue.

In my two-story house, I can’t hear a downstairs doorbell upstairs and vice-versa, so I have a mech doorbell on each floor; the circuit powered by a 16V, 30 VA transformer). While not connected to the doorbell circuit, the GC3 is mounted on the interior wall directly below one doorbell and another doorbell is located directly above a wall-mounted SP1 on the other floor.

The goal is to integrate the SkyBell HD into the GC3 sensor system via a hardwire loop. Since SkyBell does not support this integration directly by design, I’ve been looking on this forum for a work-around. So why not disable one of my mech doorbells, replace the 30 VA transformer with a 10 VA transformer, and use the GC3 and SP1 panel speakers as sound generators to circumvent SkyBell’s “1–doorbell” limitation? Here’s what I’m planning:

According to SkyBell’s documentation, their recommended doorbell circuit is one SkyBell HD (replacing a pushbutton switch at the front door), a 16V-10 VA transformer, and a mechanical doorbell. After replacing the 30 VA transformer with a 10 VA, the work-around would be:

  1. Buy:
    a) ELK-930 Relay: https://www.elkproducts.com/product-catalog/elk-930-doorbell-and-telephone-ring-detector
    b) ELK-960 Delay timer Module: https://www.elkproducts.com/product-catalog/elk-960-delay-timer-module
  2. Remove power from the doorbell’s new 10 VA transformer circuit
  3. Insert the doorbell sensing relay (ELK-930 with ELK 960 Timer Delay) into the circuit between the transformer and mech doorbell. Set the ELK-930 relay to N/C and adjust the ELK-960 timer delay as needed
  4. Hardwire a loop from the ELK-930’s Open Collector output (OUT & NEG) to the GC3’s hardwire Loop1+/Common terminal (respecting polarity)
  5. Program the GC3 to associate a new zone to the hardwire Loop1, select a binary sensor for the hardwire loop with “perimeter”, “No response”, no “transmission delay”, program the sensor to be “N/O” and select the new zone’s sounder to be a “ding-dong #2 chime”.
  6. Apply power back to the doorbell circuit

I’m expecting the GC3 and SP1 to respond as follows with SkyBell HD’s pushbutton:
A. When pushbutton is depressed, the ELK relay sends a trigger back to the GC3 via the hardwire Loop1 (timing controlled by ELK-960 Delay timer)
B. The GC3 senses that the new zone is triggered and both panels (SP1 synced to GC3) generate a “ding-dong” through their panel speakers, but do not send an alarm, an alert, or activate a siren
C. Each panel’s speaker would provide the “ding-ding” sound on both floors via the synced SP1 & GC3
D. I can keep one of the mech doorbells active within the circuit to meet SkyBell’s recommended configuration
E. And, I get to use the SkyBell HD doorbell feature as originally designed

Q1 - Should this work (no guarantee expected), just your expert opinion is requested?
Q2 - And if so, what would be the equipment code for the new hardwire zone?
Q3 - Is “perimeter” the correct setting for this new hardwire zone?
Q4 - Are the N/C (at the relay) and N/O (within new zone programming) setting correct as described above?

This solution was inspired from the “Design Your System” forum post by Ryan #2666 (Feb 28, 2014), Jason’s post #7549 (April 15, 2014) and other forums.
Thx

Should this work (no guarantee expected), just your expert opinion is requested?

This is definitely an interesting idea. I reached out to Alarm.com and while they do not have documentation stating not to use it with multiple chimes, they apparently do have many support tickets indicating that it did not work or had trouble activating chimes properly, and troubleshooting was never able to 100% fix the situation, so I would definitely follow the manufacturer recommendation.

So:

Should this work (no guarantee expected), just your expert opinion is requested?

Yes, but the 960 looks like it is what would get wired to the GC3. You would use the 930 as the trigger for the 960 to open the NC and common terminal relay. The GC3 hardwire zone would monitor this relay.

what would be the equipment code for the new hardwire zone?

Equipment code is not an option in hardwire zone programming.

Is “perimeter” the correct setting for this new hardwire zone?

No, Zone type (3) Perimeter zones will trip an immediate alarm when opened while the system is armed. You would want to use Zone Type (23) No Response Type.

Are the N/C (at the relay) and N/O (within new zone programming) setting correct as described above?

Normally Closed at the relay would mean that at rest, without trigger voltage, the circuit would be closed. You would want to monitor a Normally Closed sensor then in panel programming (you have created a NC sensor with the relay).